The present invention relates to a magnetic sheet assembly that can be used in an application of magnetic separation; and more particularly to a magnetic sheet assembly which may be removably held in intimate contact by adhesion to the surface of a device used for magnetic separation of biological molecules or cells.
Magnetic separation techniques typically involve the application of a magnetic field to separate ferromagnetic particles contained within a fluid medium. Such techniques use devices that can be divided into two general types: an internal apparatus, or an external apparatus. In the internal apparatus, the ferromagnetic collection structure is contained within the fluid medium in order to intensify the applied magnetic field and improve the resultant gradient. One example of an internal apparatus involves packing steel wool or wires (xe2x80x9ccollection structuresxe2x80x9d) into a column, wherein the column is situated adjacent to a magnet. A magnetic field is applied to the steel wires such that magnetic particles introduced into the column are attracted toward, and bind to, the steel wires. Another example of an internal apparatus involves loops of ferromagnetic wire that are inserted into a fluid medium. Drawbacks of such systems include entrapment of non-magnetic components; the potential for magnetic shielding of the collection structure therein; breakage of the collection structure during use and/or cleaning; and the requirement for cleaning or disposal of the collection structure between samples. In the external apparatus, generally the magnetic means is situated entirely externally with respect to the separation chamber. Typically, an external apparatus involves a plurality of magnets, or complex magnetic circuitry, placed around the periphery of the separation chamber; wherein the plurality of magnets, or the magnetic circuitry, produces a magnetic field gradient used to effect the magnetic separation. Drawbacks of the external systems include the need for intervention by the user to redesign the placement, positioning, or sizing of the plurality of magnets or circuitry to apply a magnetic field gradient to separation chambers of different sizes; and the additional need for manipulating multiple structures required for placement and positioning of the plurality of magnets or magnetic circuitry. Additionally, some systems use high magnetic field strengths (e.g., 3,000 gauss) which have the potential to alter biological functions of cells. A drawback shared by both currently available internal systems and external systems for magnetic separation is that such systems typically do not allow viewing of magnetic beads (e.g., as coupled to cells or molecules) during the-magnetic separation process (e.g., the magnet or electromagnet or magnetic circuitry prevent the viewing of magnetic beads during the process).
To address the need for a simple-to-use and efficient magnetic separation system, a cell culture device which can also be used for magnetic separation of cells has been disclosed in co-pending U.S. application Ser. No. 09/526,006, which has issued as U.S. Pat. No. 6,455,310 (the disclosure of which is herein incorporated by reference). However, there is a need for a magnetic sheet which can be removably adhered to such a cell culture device to provide efficiency and versatility for magnetic separation of biological cells or molecules contained therein.
Thus, there is a need for a magnetic sheet assembly that can be manufactured, shipped, and stored as a separate unit and which may be used as an accessory for magnetic separation when applied to a cell culture device.
It is a primary object of the invention to provide a simple, cost effective construction of a magnetic sheet assembly which can be in a non-adherable form, but which can be easily converted into an adherable form when it is desired to removably adhere the magnetic sheet assembly to the surface of a device for magnetic separation.
It is another object of the invention to provide a magnetic sheet assembly that can be easily handled while it is placed in a packing case for shipping to a user site, easily handled while removing it from the packing case, and easily manipulated so as to be removably adhered to the desired surface of a device for magnetic separation.
It is another object of the invention to provide a magnetic sheet assembly which remains non-adherable during packing, storage, and shipping modes, until it is desired to be removably adhered to the surface of a device for magnetic separation.
It is another object of the invention to provide a magnetic sheet, having a magnetic pole spacing and field strength that can maximize magnetic separation.
It is a further object of the present invention to provide a magnetic sheet assembly adapted to permit ready adhesion to and removal from a surface of a device for magnetic separation, while leaving substantially no adhesive residue on the surface so as to avoid impairment of subsequent microscopic analysis in the device of components (e.g., cells) which are a result of magnetic separation.
One of the novelties of the magnetic sheet assembly according to the present invention is that it allows easy fabrication (such as during cutting, packaging, and handling) of a magnetic sheet assembly adapted to permit ready adhesion to and removal from a surface of a device for magnetic separation, as well as being adapted to provide efficient magnetic separation.